The function of the normal, healthy kidney in the animal body is to act as a filter for the blood circulating through the body, to remove impurities therefrom and restore correct blood composition balance. When the kidneys cease to function, artificial kidneys can be employed in their place, such an artificial kidney comprising a flexible dialysis membrane used outside the body as a separate treatment apparatus for blood dialysis or filtration purposes. Blood from the body is circulated past one side of the membrane and special dialysis fluid is circulated past the other side of the membrane, so as to adjust and correct the blood composition by osmosis, diffusion and ultrafiltration across the membrane. A patient with deficient natural kidney function normally makes periodic use of an artificial kidney machine, in which his blood is circulated continuously past such a dialysis membrane, a small volume at a time, over a period of 4-8 hours for purification.
The kidney dialysis filters or artificial kidneys as used in such artificial kidney machines are commercially available in self-contained, cartridge form, ready for use with the machine. The filters comprise a housing containing a flexible dialysis membrane separating a blood side and a dialysate side, with inlet and outlet connections for fluid to both blood side and the dialysate side. Essentially, however, such filters are single use, disposable items which are discarded after one use on a single patient. Cleaning of the filters for reuse has been conducted by hand, but it is difficult to ensure a thorough enough cleaning, and is very time consuming and unpleasant.
In any kidney dialysis filter washing process, it is important to eliminate the risk of cross contamination, which will arise if blood particles washed out of one filter become lodged in the washing apparatus, so that they can be washed into a different filter which is subsequently washed using the apparatus, and hence contaminate the blood of the patient who subsequently uses the second filter. If a filter cartridge is washed manually, this problem does not arise. However, any attempts to wash filters automatically and successively whilst hooked up to a washing machine, are likely to run this risk, if reversal of flow of liquids through the filter housing is adopted.
It would be highly desirable to render kidney dialysis filters reusable, by the same patient because of the expense of them, and the frequency with which they need to be used. One patient may need to use the artificial kidney about 12 times per month, with a new filter unit each time.